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GATE 1994 Electronic Devices (EDC) Video solutions


1.       A small concentration of minority carriers is injected into a homogeneous semiconductor crystal at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority carriers a distance of 1 cm in 20 µsec. The mobility in cm2/volt-sec will be
a.       1000
b.      2000
c.       5000
d.      50000
                Solution :  https://www.youtube.com/watch?v=Pe9nM75oo1U
 
2.       The threshold voltage of an n-channel MOSFET  can be increased by
a.       Increasing the channel dopant concentration
b.      Reducing the channel dopant concentration
c.       Reducing the gate oxide thickness
d.      Reducing the channel length
                 Solution :  https://www.youtube.com/watch?v=1C8CrsGguu0
 
3.       The forward dynamic resistance of a junction diode varies ……………… as the forward current.
                 Solution :  https://www.youtube.com/watch?v=HfjrpzG7j8s
 
4.       The transit time of the current carriers through the channel of an FET decides its ……………. characteristics.
                 Solution : https://www.youtube.com/watch?v=vQJjmHNsn3I
5.       A p-type silicon sample has a higher conductivity compared to an n-type sample having the same dopant concentration.  (TRUE / FALSE)
                Solution :  https://www.youtube.com/watch?v=WUKXrsePs-A
 
6.       Channel current is reduced on application of a more positive voltage to the gate of a depletion mode n-channel MOSFET.  (TRUE / FALSE)
                Solution :  https://www.youtube.com/watch?v=W34kWifl15o
 
7.       Match the following :
                 Solution : https://www.youtube.com/watch?v=GWjW0DVZkSI
8.       Show that the minimum conductivity of an extrinsic silicon sample occurs when it is slightly p-type. Calculate the electron and hole concentrations when the conductivity is minimum. Given that µn = 1350 cm2/volt-sec, µp = 450 cm2/volt-sec, and the intrinsic carrier concentration, ni = 1.5 X 1010 cm-3.
9.  In the common emitter amplifier shown, the transistor has a forward current gain of 100, and a base to emitter voltage of 0.6 volts. Assume ICO to be negligible. Choose value for R1 and R3 such that the transistor has a collector current of 1 mA and a collector to emitter voltage of 2.5 volts.


     Solution :    https://www.youtube.com/watch?v=SjV5f5WC8GU